Project file wont work for me, I use cs4.
But it could be a whole bunch of possibilities, there could be something wrong with your render settings or the format you rendered it in, its hard to really know. Check out bakertut's tut on how to render and try rendering something short to see if it could be the way your renders are setup.
I'd just disable any effects you had on your video previously and just rerender it with some different settings to test it out. If that doesn't fix it, or at least help then its definetly something else.
Also, make a completely different project, just make something quickly with a bit of syncing and render that out with the same settings you used before to see if itll happen again. It's time consuming i know, but better to fix it now then have to use a temporary fix later on every time.